1. Field of the Invention
This invention relates to a device for the holding and compression of the two fragments of a fractured bone.
2. Discussion of the Background
Many devices intended to hold in compression two fragments of a fractured bone are known. U.S. Pat. No. 3,717,146 describes an intramedullary compression pin comprising threaded conical ends that are introduced into the distal and proximal fragments of the fractured bone, and which mesh with the bone tissue. U.S. Pat. No. 4,091,806 describes an intramedullary compression nail having a head in the shape of a threaded rod which sticks out from the end of one of the fragments. This head extends through a sleeve with a free end in the shape of a fork whose branches are separated by a threaded element screwed on the rod inside of the sleeve. The branches are thus driven into the walls of the medullary canal.
French patent 2,459,650 describes an intramedullary compression device able to be introduced into a hollowed-out cavity of a bone broken in two parts, a device one element of which comprises elastic elements that extend radially into the cavity and that exhibit a diameter greater than that of the cavity. These devices, which are intramedullary devices, cannot be used for epiphyseal-type fractures.
U.S. Pat. No. 3,990,438 describes a fastening and compression device for fractured bones which comprises a first part provided with cutting threads able to be anchored in the main fragment of the bone and a second threaded part to cooperate with a screw which extends on the outside of the bone and which is applied against the end of the latter to produce the axial compression. This type of screw exhibits a double drawback. On the one hand, the head of the screw does not exhibit a sufficient surface to cooperate effectively with the threading of the distal end of the screw to assure a good compression. On the other hand, in this type of screw, a bony incarceration is produced between the threads of the threaded distal part which makes the ablation of the screw very difficult.
French patent 2,633,345 describes a pin for assembly by anchoring consisting of a casing provided with several converging, sliding, expandable corollas comprising several petals ending in claws or in cutting edges. The expandable corollas, stopped by their anchoring in the interior wall of a channel, act by coming closer than by compression under the action of a screw. Such a system makes it possible effectively to hold a fractured bone in compression. However, it is fastened according to the harpoon principle, the corollas carrying the claws or the cutting edges being convergent. So long as the device is anchored in the bone by the spread claws or cutting edges, removal of the device in case of necessity cannot be performed without considerable traumatism. Considering the bony incarceration that occurs, it is not enough to proceed by unscrewing to disengage the claws or the cutting edges and remove the screw.